I. Field of the Invention
This invention relates to fluid filtering devices and, in particular, to a filtering device with a removable filter element and a rotatably securable filter head.
II. Description of the Prior Art
Fluid filtering devices which employ a rotatably securable filter head are well known in the prior art. Generally, these filtering devices include a filter head, having an inlet port and an outlet port, and which may be secured to a cylindrical fluid housing which is closed at one end and open at its other. A seal is usually provided between the fluid head and the housing to fluidly seal these two components once the filter head is rotatably secured to the housing.
The filter element is placed within the filter housing functionally between the fluid inlet and the fluid outlet such that fluid flows through the filtering media of the element. The filter element is typically cylindrical and closed at the bottom to force fluid flow through the element. The device may also be provided with one or more bypass valves which directly connect the inlet and outlet ports when pressure across the filter element becomes excessive due to a clogged or dirty filter element.
One disadvantage of such previously known filtering devices is that it is oftentimes difficult to determine when the filter element has been removed from the housing. With the filter head secured to the housing, the user is unable without disassembling the device to determine whether the filter element has been properly replaced. In addition, an unknowing user may assume that the filter element is properly positioned upon seeing the assembled device thereby possibly causing damage upon operation of the filtering system.
In an attempt to eliminate the possibility of operating the device without a filter element, filtering devices have been developed which employ a filter element integrally formed with a housing. With this construction, the device cannot be operated without a filter element in place and the absence of a filter element is apparent. However, with this construction, both the filter element and the housing must be discarded when the element becomes clogged thereby increasing replacement costs. In addition, in order to increase the pressure rating of the filtering device by substituting a fluid housing constructed of stronger materials, the filtering element must also be replaced and if such devices are used for high pressure applications the cost of replacing filter elements becomes expensive because the cost includes the cost of the housing which must be increased in strength to withstand the high pressures and which is discarded each time the filter element gets dirty.